The invention relates generally to pressure fuel servicing nozzles for mating with a standardized aircraft fueling adapter having a cylindrical extension with a plurality of indexing notches and a plurality of radially extending lock tabs.
An aircraft fuel system includes a fuel line which terminates in an exposed fueling adapter at the fuel input point. Refueling facilities include a stationary or mobile fuel supply having an extended large diameter hose or articulated pipe and various pumps for delivery of the fuel under pressure. A pressure fuel servicing nozzle is secured to the delivery end of the fuel hose or pipe and is mechanically configured to engage and receive the fueling adapter. The fuel servicing nozzle is required to perform several basic mechanical functions which include mechanically engaging and locking with the fueling adapter, providing a high pressure fuel seal between the fuel delivery hose and the aircraft fuel system, and properly valving the fuel flow between the fuel system and the aircraft to provide open flow and closed seal conditions to facilitate fueling and the termination of fueling. In addition to these basic functions, modern fuel servicing nozzles provide various safety mechanisms directed toward the prevention of fuel spillage and leakage. This is critical to the operation of such refueling systems due to the highly volatile and flammable character of aircraft fuels. One such safety mechanism provides an interlock within the fuel service nozzle which prevents opening a flow control poppet valve until the nozzle has completed proper mechanical and sealing engagement with the fueling adapter.
Referring to FIG. 1, a standardized fueling adapter 2 for commercial and military aircraft is shown. The fueling adapter 2 includes a cylindrical extension 4 with three rectangular shaped indexing slots 6 having flat engaging surfaces 7. Three lock tabs 8 extend radially outwardly from the cylindrical extension 4 and an adapter poppet valve 10 is biased in a closed position to prevent fuel flow. Due to the physically demanding operating environment of refueling an aircraft, which involves handling relatively long and heavy fueling hoses under a variety of situational urgencies as well as all weather conditions, the engagement surfaces of the lock tabs 8 are usually ramped and radiused to enable an operator to readily engage and rotate the fuel nozzle onto the fueling adapter 2, wherein scuffing or binding of the engagement mechanism of the fuel nozzle against the lock tabs 8 is reduced. Another benefit of providing ramped and radiused lock tabs 8 is the reduction in wear of the engagement mechanism.
Generally, existing fuel servicing nozzles comprise a rotating collar rotatably mounted upon a nozzle body which receives and locks with the fueling adapter to provide engagement. An interlock system prevents the opening of the flow control poppet valve within the nozzle body until mechanical engagement as evidenced by the rotational position of the collar is obtained. A receiving portion of the fuel nozzle receives and engages the fueling adapter 2, and the interlock system includes an interlock plate which prevents rotation of the collar in the absence of the insertion of the fueling adapter 2. The interlock plate is generally a flat ring shaped member which is biased onto a bayonet ring embedded within the collar. When the fuel nozzle is not connected to the fueling adapter 2, the engagement surfaces of the interlock plate abut against the blocking walls extending outwardly from the inner surface of the bayonet ring.
To connect the fuel nozzle to the fueling adapter 2 an operator aligns three locating pins of the fuel nozzle with the indexing slots 6 of the fueling adapter 2. When the fuel nozzle is aligned, the fuel nozzle can be pushed into the fueling adapter 2, thereby depressing the interlock plate away from the inner surface of the bayonet ring to clear the blocking wall and allowing the collar to be rotated about the nozzle body. After full rotation of the collar, an operating handle is now free to be rotated to open the flow control poppet valve. Of particular note is that the ramped and radiused lock tabs 8 may allow rotation of the collar prior to full depression of the interlock plate. This partial depression of the interlock plate by an incomplete engagement allows the start of the rotation of the collar. Furthermore, the interlock system is designed to disengage under a less than full depression of the interlock plate because of timing issues dealing with the physical relationship of the axial movement of the interlock plate with respect to the rotational movement of the collar as defined by the ramped and radiused lock tabs. Thus, the height of the blocking surface is. usually substantially less than the clearance provided by a full depression of the interlock plate.
The features discussed above to allow easy coupling of the fuel nozzle to the fueling adapter 2 effects the safety of the connection because the nozzle body may not be held in the correct position when the collar is being rotated about the fueling adapter during both connection and disconnection. A situation may arise where the fuel nozzle is connected to the fueling adapter 2 where the longitudinal axis of the fuel nozzle is slightly skewed with the longitudinal axis of the fueling adapter 2. As a result, a gap may exist in the fuel seal between the contacting surfaces of the fuel nozzle and fueling adapter 2. If the improper connection sufficiently depresses the interlock plate to clear the blocking walls of the bayonet ring, the interlock system may be defeated and an operator may be able to rotate the operating handle and open the fuel nozzle, and a dangerous fuel spill may result.
In another possible situation, the fuel nozzle may be properly aligned and coupled to the fueling adapter 2, but the lock tabs 8 of the fueling adapter 2 may be worn to the extent that the fuel nozzle may be removed from the fueling adapter 2 under an unsafe condition such as when the collar assembly is not fully rotated in the closed direction with respect to the body when disconnection from the fueling adapter 2 occurs, due to worn lock tabs 8 which exhibit thinning in critical regions. In this case, the interlock plate does not return to the locking condition and the abutting surfaces of the bayonet ring and the interlock plate are not mated. With the interlock feature so defeated, the collar can be rotated back to the open position when not attached to the fueling adapter 2, thereby allowing the operating handle to then be rotated to open the nozzle.
Another problem which may arise in existing fuel servicing nozzles is the unintentional disengagement of the flow control poppet valve from the fully open position to an intermediate open position during the refueling process. When the fuel nozzle is connected to the fueling adapter 2, rotation of the operating handle causes the flow control poppet valve to be pushed into the fueling adapter 2 and consequently pushes open the corresponding spring loaded, adapter poppet valve 10. The spring from the adapter poppet valve maintains both poppet valves in intimate contact and applies a force in the upstream direction that keeps the internal components of the fuel nozzle in the fully open position, due to an over-center locking condition of a crankshaft. During relatively high flow rates, the adapter poppet valve 10 may be pushed further in the downstream direction by the flowing fuel impinging on the adapter poppet valve 10. Intimate contact between the poppet valves is disrupted, and the flow control poppet valve no longer receives a force in the upstream direction from the adapter poppet valve. Consequently, the flow control poppet valve and related internal components are free to rotate and/or travel to a position other than the fully open position.
Typically, it is highly desireable to refuel an aircraft as quickly as possible. This is particularly important in the commercial airline industry where market conditions are extremely competitive and in the military where combant readiness of an aircraft is highly desireable. If the operating handle is unknowingly disengaged from the fully open position during refueling, which may occur during an abrupt increase in fuel flow, fuel flow may be reduced and the period for the refueling may be increased unless the operator rotates the operating handle back to the fully open position.
Thus, there remains a need. for an improved aircraft fuel servicing nozzle designed to connect and disconnect to a standardized fueling adapter mounted on an airframe and connected to an internal fuel manifold and tank system. In particular, a reliable, rugged, and safe fuel servicing nozzle is desireable which is light weight and easy to operate.
In accordance with the present invention, an exemplary embodiment of an improved aircraft fuel servicing nozzle is provided which is designed to connect and disconnect with a standardized fueling adapter mounted on an airframe and connected to an internal fuel manifold and tank system. The present invention achieves the objective of connecting and disconnecting with a fueling adapter, such as the version shown in FIG. 1, in a reliable, rugged, and safe manner and yet being relatively light weight and easy to operate.
The fuel servicing nozzle comprises a nozzle body having an outer surface an interior passage. A collar assembly is rotatably supported upon the outer surface of the nozzle body. A valve operating handle is rotatively coupled to the nozzle body. A plurality of locating pins extend outwardly from a distal base of the nozzle body. It is noted that xe2x80x9cdistalxe2x80x9d refers to a downstream end and xe2x80x9cproximalxe2x80x9d refers to an upstream end of the fuel servicing nozzle. The fuel nozzle is aligned onto the fueling adapter by fitting the locating pins into the indexing notches of the fueling adapter. The fuel servicing nozzle further includes an interlock plate biased towards an inner surface of a bayonet ring, and the interlock plate includes engagement surfaces. Primary interlock stops extend outwardly from the inner surface of the bayonet ring a distance a, and adjacent to each primary interlock stop is a secondary interlock stop extending outwardly from the inner surface of the bayonet ring a distance b, where b is greater than a.
When the fuel servicing nozzle is not connected to the fueling adapter, rotation of the collar assembly relative to the nozzle body is prevented by the engageable surfaces of the interlock plate abutting against the primary interlock stops. When the fuel nozzle is inserted into the fueling adapter, the interlock plate is depressed toward the nozzle body and the mechanical interference between the primary interlock stops and engageable surfaces is cleared such that the collar assembly is free to partially rotate about the nozzle body and fueling adapter. As in existing fuel nozzles, partial depression of the interlock plate is adequate to clear the primary interlock stops. Thus, an operator is able to perform the steps of inserting, aligning, and partially rotating the collar assembly with relative ease. With the collar assembly attached to the fueling adapter, the operator has an opportunity to more carefully align the fuel nozzle and fully depress the interlock plate to clear the secondary stops and rotate the collar assembly to the fully secured position, wherein a proper seal is formed between the fuel nozzle and fueling adapter. After full rotation of the collar, the operating handle may now be rotated to open the nozzle poppet valve and to allow fuel flow. If the operator is unable to properly align the fuel nozzle and clear the secondary interlock stops, further rotation of the collar assembly towards the secured direction is prevented, and the operator will not be able to rotate the operating handle to open the nozzle poppet valve. Of course, the steps of partially rotating and fully rotating the collar assembly may appear seamless, particularly with an experienced operator.
Another feature of the fuel nozzle of the present invention is that the interlock system prevents the opening of the flow control poppet valve when the fuel nozzle is coupled to an unsafe fueling adapter having worn lock tabs. The lock tabs may adequately. depress the interlock plate to clear the primary interlock stops. However, the lock tabs may not be sufficiently thick to fully depress ,the interlock plate to clear the secondary interlock stops, thereby preventing full rotation of the collar assembly and rotation of the operating handle to open the nozzle poppet valve. Thus, the potential problem of decoupling the fuel nozzle from the fueling adapter with the flow control poppet valve in an open position and with fuel flowing may be avoided.
The fuel nozzle of the present invention may further include a bias member to maintain the flow control poppet valve in the fully open position to maximize the flow rate of fuel and minimize refueling time. In other words, once the operating handle is rotated to the fully open position, the bias member maintains the flow control poppet valve in the fully open position under various operating conditions which may otherwise cause the flow control poppet valve to undesirably move towards the close direction. If the flow control poppet valve is unknowingly disengaged from the fully open position during refueling, and an operator fails to rotate the operating handle back to the fully open position, fuel flow may be reduced and the refueling time may be increased.
In accordance with the exemplary embodiment, the fuel service nozzle includes a valve stem slidingly guided by a sleeve, and a proximal end of the valve stem is connected to a crank arm of a crankshaft by a V-shaped arm, while the distal end of the valve stem is connected to the flow control poppet valve. Rotation of an operating handle rotates the crankshaft and causes the V-shaped arm to translate a rotating motion to an axial motion of the valve stem. The V-shaped arm allows for limits of the rotation of the crankshaft, wherein the limits are xe2x80x9cpast top dead centerxe2x80x9d and xe2x80x9cpast bottom dead centerxe2x80x9d. As the operating handle is rotated to the fully open position, the crankshaft passes xe2x80x9cbottom dead centerxe2x80x9d to the xe2x80x9cpast bottom dead centerxe2x80x9d position and remains in the xe2x80x9cpast bottom dead centerxe2x80x9d position due to the adapter poppet valve directing an upstream directed force upon the flow control poppet valve. When intimate contact between the poppet valves is disrupted, a bias member provides the force required to maintain the flow control poppet valve in the fully open position. In an exemplary embodiment, the bias member includes a spring disposed at a proximal end of the sleeve and is compressed between the proximal end of the sleeve and a proximal region of the valve stem when the flow control poppet valve is in the fully open position. As the spring is compressed, a force in the upstream direction is directed to the valve stem, wherein an upstream force upon the valve stem is provided by compression of the spring.
Other objects, features, and advantages of the present invention will become apparent from a consideration of the following detailed description.